Public Health Significance of Urban Pests
305
Ticks
304
10.1. Introduction
Ticks transmit more cases of human disease than any other arthropod vector in Europe and North America. They are also important worldwide as disease vectors to people and
domestic animals, and they cause substantial economic losses, both by transmitting dis- ease and by direct negative effects on cattle Jongejan Uilenberg, 2004. Lyme borreliosis
LB, in particular, is the most commonly reported vector-borne disease in both Europe and North America Steere, Coburn Glickstein, 2005. In Europe, Tick-Borne
Encephalitis is also prevalent, especially in central and eastern Europe, while in North America, Rocky Mountain spotted fever RMSF, caused by a rickettsial agent, is respon-
sible for a few hundred to over a thousand cases a year. In addition to their importance as disease vectors, some hard tick species can directly cause adverse effects, such as tick
paralysis, a toxicosis systemic poisoning due to toxic salivary proteins. Similarly, soft ticks can provoke severe allergenic bite reactions in people IgE-mediated type-I allergy.
The response to tick-borne diseases TBDs in the United States has been substantial, including federally sponsored research programmes, public health programmes within
individual states partly funded by the CDC [United States Centers for Disease Control and Prevention] and several smaller programmes funded by states, localities and non-
profit-making organizations. States with a high incidence of disease have numerous public education programmes, and several novel methods of tick and disease manage-
ment have been developed Stafford Kitron, 2002. However, coordination and eva- luation of programmes is spotty, and the incidence of disease remains high in many loca-
les and has increased nationwide Piesman Gern, 2004. Ecological differences in transmission dynamics from site to site mean that the approach to management needs to
be tailored to conditions at each locale. Methods for developing effective IPM program- mes and evaluations of efficacy remain high priorities Ginsberg Stafford, 2005.
The situation in Europe is different in that national reporting strategies differ among countries Table 10.1, and little has been done to routinely implement measures that pro-
tect individuals against tick bites or TBDs. Some notable exceptions are vaccination against T BE Nuttall Labuda, 2005 and the use of skin repellents in some areas.
Fabrics impregnated with acaricides agents that kill ticks and mites, such as perme- thrin, are widely unknown and difficult to procure, even for personnel occupationally
exposed to tick-infested areas of endemic TBDs. So far, few research efforts have been initiated to reduce tick populations by ecological changes, biological control or IPM.
10.2. Ticks of Europe and North America
Ticks are arachnids the class Arachnida includes spiders, scorpions, ticks and mites in the subclass Acari, which includes mites and ticks. There are three families of ticks
Barker Murrell, 2004: the hard ticks, Ixodidae 713 species, which includes most ticks of medical importance to people; the soft ticks, Argasidae 185 species, which includes a
few species that transmit diseases to humans; and Nuttalliellidae, which includes just one species from Africa with no known medical importance.
Table 10.1. TBDs in Europe to be notified to national health authorities, as of 2005 Country locale
TBE CEE Lyme borreliosis
Other diseases
Albania - Endemic
- Endemic -
Austria +
+ Only meningoencephalitis -
caused by Lyme borreliosis Belarus
+ +
Tularaemia, Q fever, tick-borne haemorrhagic fevers
Belgium -
- Endemic -
Bosnia and Herzegovina -
+ CCHF
Bulgaria - Endemicity
- Endemic CCHF
status unclear Croatia
+ +
Tick-borne tularaemia, ehrlichiosis, human granulocytic anaplasmosis
Czech Republic +
+ -
Denmark - Not endemic
+ Neuroborreliosis only -
Estonia +
+ Tick-borne tularaemia
Finland +
+ France
- Endemic - Endemic
- Germany
+ + Only the federal states
- of Brandenburg, Mecklenburg-
Western Pomerania, Berlin, Lower Saxony, Saxony-Anhalt
and Thuringia about 25 coverage of population
Greece - Not endemic
+ -
Hungary +
+ -
Ireland - Not endemic
- Endemic Louping ill
Italy +
+ -
Latvia +
+ Tick-borne tularaemia
Lithuania +
+ Tick-borne tularaemia
Luxembourg - Not endemic
+ Netherlands
- - Endemic
- Norway
+ +
- Poland
+ +
- Portugal
- + -
Republic of Moldova - Endemic
- Endemic -
Romania +
+ MSF
Russian Federation +
+ Tularaemia, Q fever, tick-borne
haemorrhagic fevers Serbia
+ +
- Slovakia
+ +
- Slovenia
+ +
HGE Spain
- - Endemic
- Sweden
+ - Endemic
- Switzerland
+ - Endemic
- The former Yugoslav
- +
- Republic of Macedonia
Ukraine +
+ Tularaemia, Q fever, tick-borne
haemorrhagic fevers United Kingdom
- + Scotland only
- Note.
-: not notifiable disease; +: disease notifiable by national health organisations. Source:
The information in this table has been provided by M.K. Faulde and is based on official civil and military country sources.
Public Health Significance of Urban Pests
Ticks
307 306
Endemic tick species in Europe can be peridomestic or can be associated with pets and farm animals Table 10.2. European ticks that can infest buildings in urban environ-
ments include: the ixodid brown dog tick, Rhipicephalus sanguineus, as far north as sou- thern Germany; and the argasids: the European pigeon tick, Argas reflexus associated
with pigeons, and the fowl tick, Argas persicus associated with poultry in south-eastern Europe. Long-term infestations with brown dog ticks can occur in human dwellings, if
control efforts are neglected Gothe, 1999. The only survey thus far for European pigeon ticks was performed in the city of Berlin, where more than 200 infested buildings were
discovered between 1989 and 1998 Dautel, Scheurer Kahl, 1999. Most of the infesta- tions were found in older buildings constructed before 1918. Control is difficult and
requires professional expertise and time.
Recent studies in Germany have shown increases in urban and periurban collections of castor-bean ticks, IxodesricinusMehnert, 2004. According to studies conducted in north-
eastern Germany, Lyme borreliosis LB is most often acquired in city parks and gardens near forests Ammon, 2001; Anonymous, 2005a. Other ticks, such as the soft tick
Ornithodoros erraticus
, and the hard ticks Dermacentor spp., Hyalomma spp. and Haemaphysalis
spp., are associated with pigs, sheep and cattle and are known vectors of both animal and human disease agents. They usually do not infest houses, but can be
found in stables and in houses that incorporate stables. The most common hard ticks that regularly bite people in North America Table 10.3
include: the black-legged or deer tick, Ixodes scapularis, in eastern and central North America; the western black-legged tick, Ixodes pacificus, in west coastal areas; the
American dog tick, Dermacentor variabilis, in the east and Midwest; the Rocky Mountain wood tick, Dermacentor andersoni, in the Rocky Mountain region; the Pacific Coast tick,
Dermacentor occidentalis
, on the Pacific coast; and the lone star tick, Amblyomma ameri- canum
, in eastern and central North America. The brown dog tick attaches to dogs and can be found in the home, but rarely attaches to people. The primary soft ticks that affect
people are Ornithodoros spp. in western areas. These ticks are found primarily in natural areas and are often encountered by recreatio-
nal users of parks and woodlands Ginsberg Ewing, 1989. However, increasing sub- urbanization around major urban centres has resulted in substantial contact between peo-
ple and ixodid ticks, and most disease transmission from ticks to people occurs in the peridomestic environment Maupin et al., 1991. Some nidicolous species including soft
ticks, such as Ornithodoros spp. are found in animal nests in rustic cabins and can trans- mit pathogens such as relapsing fever borreliae to recreational users of these dwellings
Barbour, 2005.
10.3. Tick-borne diseases